Abstract
Minimum-energy operation is a function of the gate-size ratio at different values of the power supply. In this brief, circuit designs that are capable of responding to changes in the power supply voltage and adjusting the gate-size ratio accordingly for minimum-energy operation are presented. The dynamically adjustable gate-size ratio allows the gate to preserve a symmetric voltage transfer characteristic at both normal supply and subthreshold operations. This translates to maximized noise margins over the whole range of the supply voltage. Simulation results show that the performance of the proposed circuits is superior to fixed gate sizes aimed at fixed-supply operation. The proposed adaptive gate circuit designs provide up to six times reduction in the power-delay product in comparison with the fixed-size gate. The proposed designs represent a complete solution for circuits that have to adapt to wide variations in the power supply while preserving relative characteristics.